As is well known to those skilled in the art, certain power tools require precision guiding of work pieces therein in order to produce desired geometries, tolerances and configurations. Thus, for example, conventional power driven equipment such as table saws, router tables and the like have included at or on guiding surfaces one or more longitudinally disposed slots adapted for mated fitting with guiding members that thereby may be guided rectilinearly. In addition, in certain uses, provision must be made to lock the guiding member in a desired position within the guide slot while providing for its ready release. The geometries of the guiding members must be closely correlated with the dimensions of the slots so as to avoid binding, wobble or other tracking errors. The dimensions of such slots often conform to industry-wide standards, albeit within a broad range of tolerances. Dimensional variations within this tolerance range from manufacturer to manufacturer, and from machine to machine often result in a poor fit between a particular guide member and a given slot, thus producing unacceptable occurrences of the aforementioned tracking errors.
To accomplish the foregoing, there have previously been proposed a variety of configurations including the formation of the guiding member in an extended longitudinal geometry that fits within the guiding slots. Due to the aforementioned variations in slot dimensions, it was typically necessary to machine the guiding member to exacting tolerances in order to produce a customized fit between the guide member and a particular guide slot in an effort to reduce tracking errors. In addition to being relatively expensive to manufacture, such a custom guide member would also become one of a kind, and could not be readily transferred to another machine whose guide slots differed in geometry from those to which it had previously been fitted. In many cases, the guide member was constructed from wood, which was chosen for its low cost, widespread availability, and its relative ease of fabrication on readily available and inexpensive woodworking equipment. This, however, imposed an additional limitation brought about by the dimensional instability typical of most woods which is caused by variations in ambient temperature and humidity. Thus, under one set of atmospheric conditions, such a wooden guide member might very well fit perfectly in its intended guide slot, whereas under a different set of weather conditions it might bind or wobble excessively.
As mentioned previously, certain uses require that the guide member be disengageably locked within the guide slot for stationary applications. Since the aforementioned custom fitted guide members have no provision for such a locking action, they could not be used for these purposes. Other proposals exist to accomplish this locking operation, but they typically are usable for this purpose only, and cannot be used for those applications mentioned previously which require a close tolerance rectilinear movement of the guiding member along its associated guide slot. Additionally, some of these other proposals include levers or similar elements disposed above or below the guide member to disengageably lock the member in the guide slot. Such extensions potentially interfere with the full use of the equipment, or limit its use to a single application.
In view of the foregoing, it is apparent that there has continued to be a need for an improved positionable guiding member which singly can operate with a high degree of alignment accuracy over a wide range of guide slot geometries, while also providing the capability of being disengageably locked at any position in such guide slots. Additionally, the need continues to exist for such a guiding member which also embodies simplicity of operation, does not encroach upon equipment working surfaces, and is relatively inexpensive and simple to manufacture.